The invention relates to a device for collecting particles that have a strong electron affinity, particularly explosive particles from a gas.
The increasing use of explosives in terrorist attacks is a generally known security problem. Protecting civilian and military infrastructures from individuals and vehicles that transport improvised explosive devices currently represents a major challenge. Indications of concealed explosive material can be obtained with the aid of “BULK methods” (X-ray, terahertz, NMR detection). Another method for evidence collection methods is classed as “trace detection”. In trace detection, gases that emanate from the concealed explosives are detected. In conjunction with sniffer dogs, this method relies primarily on ion mobility spectrometers (IMS) that can detect trace gases in a concentration range of (10−9) ppb. In IMS detection of explosives, particular use is made of fact that the molecular structures of most explosives include nitro groups, which have a strong electron affinity. An important distinguishing criterion with respect to other substances that occur in trace amounts is therefore that explosives have a high tendency to form negative ions. These substances can then be differentiated further in IMS measurement via various runtimes in the IMS drift tube. One difficulty with detecting gas in this way is that many explosives, especially materials that are used extensively in military applications, have an exceptionally low vapour pressure, which severely hinders their detectability using gas detection methods.